When agents at the Drug Enforcement Administration learned a suspect was using PGP to encrypt documents, they persuaded a judge to let them sneak into an office complex and install a keystroke logger that recorded the passphrase as it was typed in.

A decade ago, when the search warrant was granted, that kind of black bag job was a rarity. Today, however, law enforcement agents are encountering well-designed encryption products more and more frequently, forcing them to invent better ways to bypass or circumvent the technology.